Agreed with getting the X4 975...generally speaking, most games will not make proper use of all 6 cores on an X6. So, it's better to get the higher clocked CPU.
Good choice on the motherboard.

I used to run a Crosshair IV Formula and absolutely loved it. One of the the best AM3 motherboards out there. If you decide to get into the overclocking scene, this is a great board for that - very much geared toward the overclockers. Also, IIRC the CH4 will support BD when it comes out. So, it's just a simple BIOS update if you want to later upgrade to the Bulldozere CPU's.
Lastly, +1 on dma0991's comment about the WD green drive. If you can work an SSD into your budget, that would be much better. If not, the WD Caviar Blacks are excellent mechanical drives too.